A semiconductor integrated circuit (hereinafter referred to as IC) is usually produced by slicing a high purity silicon single crystal to form a semiconductor wafer, mounting an integrated circuit on the surface using a means such as etching, shaving the back surface of the semiconductor wafer by grinding, etching, lapping or the like, thereby to reduce the thickness to about 200 to 400 .mu.m, and dicing the wafer to form a chip. To sum up, after the completion of formation of IC, a chip is formed in a dicing step after going through four steps, that is, a step of applying an adhesive tape to the semiconductor wafer surface, a step of grinding the back surface of the semiconductor wafer, a step of peeling off the adhesive tape, and a step of washing the semiconductor wafer surface. When the semiconductor wafer is fed between these production steps, the semiconductor wafer is usually fed in the state of being encased in a cassette. That is, in the respective steps, a unit operation of taking out from the cassette and encasing it into the cassette is repeated. Such an operation can be not only the larger cause of breakage of a wafer because of the recent tendency of a reduction in thickness of the layer and an increase in diameter, but also the cause of complication of the steps and loss of the working time.
With the reduction in size of a semiconductor chip, a tendency of a reduction in thickness of a wafer is increased and a conventional thickness (about 200 to 400 .mu.m) of a wafer after grinding the back surface was reduced to about 150 .mu.m, depending on the kind of the chip. Also regarding the size, a conventional diameter (maximum 8 inch) tends to be increased to 12 inch, furthermore to 16 inch. Under the circumstance of the reduction in thickness and increase in diameter of the semiconductor wafer, the semiconductor wafer having the back surface subjected to grinding is liable to cause war page. In case that the adhesive tape is applied on the surface of the wafer, its tendency is increased by a tension of the adhesive tape. For the reason, the semiconductor wafer whose thickness is reduced after grinding contacts with an encasing port of the cassette in case of containing in the cassette and, therefore, the semiconductor wafer is liable to be broken only by applying a small impact.
In the grinding step of the back surface of the semiconductor wafer, a wafer surface protecting adhesive tape is applied on the wafer surface for the purpose of protecting IC formed on the surface of the semiconductor after and preventing the semiconductor wafer from breaking by a grinding stress. Since the adhesive tape becomes unnecessary after the completion of the grinding of the wafer back surface, it is peeled off from the wafer surface by using an adhesive tape peeling device. As a peeling method, for example, Japanese Patent Kokai Publication No. 28950/1990 discloses a method of applying a tape having a strong adhesive force referred to as a release tape on the base film surface of an adhesive tape applied on the semiconductor wafer surface and peeling the adhesive tape via the release tape. However, under the circumstance of the reduction in thickness and increase in diameter of the semiconductor wafer, the semiconductor is liable to be broken when the semiconductor wafer with severe warp is fixed to a chuck table of a peeling device or the adhesive tape is peeled off from the semiconductor wafer, as described above.
To prevent the breakage of the wafer when the adhesive tape is peeled off from the semiconductor wafer surface, there is suggested a film for surface protection wherein the peelability is improved. For example, Japanese Patent Kokai Publication No. 189938/1985 describes a method of applying an adhesive film comprising a light transmitting substrate and a pressure-sensitive adhesive having a property capable of curing by light irradiation to form a three-dimensional network, said pressure-sensitive adhesive being provided on said substrate, on the wafer surface in case of grinding the back surface of the semiconductor wafer, irradiating this adhesive film with light after grinding, and peeling off the adhesive film without causing the breakage of the wafer. However, the pressure-sensitive adhesive (adhesive layer) having a property capable of curing by light irradiation to form a three-dimensional network, which is disclosed in the invention, is an adhesive layer capable of polymerizing by the radical polymerization. Therefore, when oxygen is entrapped between the wafer and adhesive layer, the curing reaction does not proceed sufficiently by the polymerization inhibition effect of oxygen and the wafer surface is sometimes contaminated with the uncured adhesive having a low cohesive force at the time of peeling after grinding the wafer back surface. Since the wafer surface on which an integrated circuit is mounted has a complicated irregularity, it is very difficult to apply the adhesive film without entrapping any air (oxygen). To make a system wherein oxygen is removed for applying, it is necessary to newly dispose a device. Contamination caused by such an adhesive can be removed by washing with a solvent, sometimes, but can not completely be removed at present in almost all of cases. According to this method, any advantage cannot be found with respect to the prevention of the breakage of the wafer and reduction of the working time when the wafer is fed to the adhesive tape peeling step after grinding the wafer back surface.
As described above there has been required a method of producing a semiconductor wafer, which can maintain the contamination resistance of the wafer surface and prevention of the breakage of the wafer back surface at the time of grinding at the same level as that of the prior art under the circumstance of the increase in bore diameter and reduction in thickness of the semiconductor wafer, and does not cause the breakage of the wafer when the adhesive tape is peeled off and the wafer is fed between the respective processing steps, and also which can reduce the working time.